MacUIM is a Mac OS X input method using uim. This means uim can be used on MacOS X.
Japanese uim wiki
Japanese uim wiki is a wiki for information about uim in Japanese.
Input Method related
SCIM is abbreviation of Smart Common Input Method platform.
IIIMF is abbreviation of Internet/Intranet Input Method Framework.
Multilingualization Library, so-called m17n-lib. You can use input part of m17n-lib with uim.